arXiv subjects

Thomas C. Schmidt

Publications and source records attributed to Thomas C. Schmidt.

At least 55 records · Page 3Linked to original sources

arXiv2022

On the Interplay between TLS Certificates and QUIC Performance

In this paper, we revisit the performance of the QUIC connection setup and relate the design choices for fast and secure connections to common Web deployments. We analyze over 1M Web domains with 272k QUIC-enabled services and find two worrying results. First, current practices of creating, providing, and fetching Web certificates undermine reduced round trip times during the connection setup since sizes of 35% of server certificates exceed the amplification limit. Second, non-standard server implementations lead to larger amplification factors than QUIC permits, which increase even further in IP spoofing scenarios. We present guidance for all involved stakeholders to improve the situation.

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arXiv2022

IPv6 over Bluetooth Advertisements: An alternative approach to IP over BLE

The IPv6 over Bluetooth Low Energy (BLE) standard defines the transfer of IP data via BLE connections. This connection-oriented approach provides high reliability but increases packet delays and requires substantial overhead to manage BLE connections. To overcome these drawbacks we present the design and implementation of IPv6 over BLE advertisements, a standard-compliant connection-less approach. We deploy our proposal on low-power IoT hardware and comparatively measure key network performance metrics in a public testbed. Our results show that IP over BLE advertisements offers network performance characteristics complementary to IP over connection-based BLE, trading lower reliability for shorter~latency.

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arXiv2022

Delay-Tolerant ICN and Its Application to LoRa

Connecting long-range wireless networks to the Internet imposes challenges due to vastly longer round-trip-times (RTTs). In this paper, we present an ICN protocol framework that enables robust and efficient delay-tolerant communication to edge networks. Our approach provides ICN-idiomatic communication between networks with vastly different RTTs. We applied this framework to LoRa, enabling end-to-end consumer-to-LoRa-producer interaction over an ICN-Internet and asynchronous data production in the LoRa edge. Instead of using LoRaWAN, we implemented an IEEE 802.15.4e DSME MAC layer on top of the LoRa PHY and ICN protocol mechanisms in RIOT OS. Executed on off-the-shelf IoT hardware, we provide a comparative evaluation for basic NDN-style ICN [60], RICE [31]-like pulling, and reflexive forwarding [46]. This is the first practical evaluation of ICN over LoRa using a reliable MAC. Our results show that periodic polling in NDN works inefficiently when facing long and differing RTTs. RICE reduces polling overhead and exploits gateway knowledge, without violating ICN principles. Reflexive forwarding reflects sporadic data generation naturally. Combined with a local data push, it operates efficiently and enables lifetimes of >1 year for battery powered LoRa-ICN nodes.

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arXiv2022

Secure Time-Sensitive Software-Defined Networking in Vehicles

Current designs of future In-Vehicle Networks (IVN) prepare for switched Ethernet backbones, which can host advanced LAN technologies such as IEEE Time-Sensitive Networking (TSN) and Software-Defined Networking (SDN). In this paper, we present an integrated Time-Sensitive Software-Defined Networking (TSSDN) architecture that simultaneously enables control of synchronous and asynchronous real-time and best-effort communication for all IVN traffic classes. Despite the central SDN controller, we can validate that control can operate without a delay penalty for TSN traffic, provided protocols are properly mapped. We demonstrate how TSSDN adaptably and reliably enhances network security for in-vehicle communication. A systematic investigation of the possible control flow integrations with switched Ether-networks reveals that these strategies allow for shaping the attack surface of a software-defined IVN. We discuss embeddings of control flow identifiers on different layers, covering the range from a fully exposed mapping to deep encapsulation. We experimentally evaluate these strategies in a production vehicle, which we map to a modern Ethernet topology. Our findings indicate that visibility of automotive control flows on lower network layers enables isolation and access control throughout the network infrastructure. Such a TSSDN backbone can establish and survey trust zones within the IVN and reduce the attack surface of connected cars in various attack scenarios.

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arXiv2022

Dynamic Clock Reconfiguration for the Constrained IoT and its Application to Energy-efficient Networking

Clock configuration takes a key role in tuning constrained general-purpose microcontrollers for performance, timing accuracy, and energy efficiency. Configuring the underlying clock tree, however, involves a large parameter space with complex dependencies and dynamic constraints. We argue for clock configuration as a generic operating system module that bridges the gap between highly configurable but complex embedded hardware and easy application development. In this paper, we propose a method and a runtime subsystem for dynamic clock reconfiguration on constrained Internet of Things (IoT) devices named ScaleClock. ScaleClock derives measures to dynamically optimize clock configurations by abstracting the hardware-specific clock trees. The ScaleClock system service grants portable access to the optimization potential of dynamic clock scaling for applications. We implement the approach on the popular IoT operating system RIOT for two target platforms of different manufacturers and evaluate its performance in static and dynamic scenarios on real devices. We demonstrate the potential of ScaleClock by designing a platform-independent dynamic voltage and frequency scaling (DVFS) mechanism that enables RIOT to autonomously adapt the hardware performance to requirements of the software currently executed. In a use case study, we manage to boost energy efficiency of constrained network communication by reducing the MCU consumption by 40 % at negligible performance impact.

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arXiv2022

The Race to the Vulnerable: Measuring the Log4j Shell Incident

The critical remote-code-execution (RCE) Log4Shell is a severe vulnerability that was disclosed to the public on December 10, 2021. It exploits a bug in the wide-spread Log4j library. Any service that uses the library and exposes an interface to the Internet is potentially vulnerable. In this paper, we measure the rush of scanners during the two months after the disclosure. We use several vantage points to observe both researchers and attackers. For this purpose, we collect and analyze payloads sent by benign and malicious communication parties, their origins, and churn. We find that the initial rush of scanners quickly ebbed. Especially non-malicious scanners were only interested in the days after the disclosure. In contrast, malicious scanners continue targeting the vulnerability.

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arXiv2022

Long-Range ICN for the IoT: Exploring a LoRa System Design

This paper presents LoRa-ICN, a comprehensive IoT networking system based on a common long-range communication layer (LoRa) combined with Information-Centric Networking (ICN) principles. We have replaced the LoRaWAN MAC layer with an IEEE 802.15.4 Deterministic and Synchronous Multi-Channel Extension (DSME). This multifaceted MAC layer allows for different mappings of ICN message semantics, which we explore to enable new LoRa cenarios. We designed LoRa-ICN from the ground-up to improve reliability and to reduce dependency on centralized components in LoRa IoT scenarios. We have implemented a feature-complete prototype in a common network simulator to validate our approach. Our results show design trade-offs of different mapping alternatives in terms of robustness and efficiency.

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arXiv2022

WIP: Exploring DSME MAC for LoRa -- A System Integration and First Evaluation

LoRa is a popular wireless technology that enables low-throughput (bytes) long-range communication (km) at low energy consumption (mW). Its transmission, though, is on one side prone to interference during long on-air times, and on the other side subject to duty cycle restrictions. LoRaWAN defines a MAC and a vertical stack on top of LoRa. LoRaWAN circumvents the above limitations by imposing a centralized network architecture, which heavily reduces downlink capacity and prevents peer-to-peer communication. This makes it unusable for many deployments. The Deterministic and Synchronous Multichannel Extension (DSME) of IEEE 802.15.4e benefits of time-slotted communication and peer-to-peer communication and has the potential to overcome LoRaWAN limitations. In this work, we implement DSME on top of LoRa in the open source IoT OS RIOT and open the field for first evaluation experiments on real hardware. Initial results indicate that DSME-LoRa not only enables reliable peer-to-peer communication for constrained IoT devices, but also scales with an increasing number of nodes.

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arXiv2022

Secure and Authorized Client-to-Client Communication for LwM2M

Constrained devices on the Internet of Things (IoT) continuously produce and consume data. LwM2M manages millions of these devices in a server-centric architecture, which challenges edge networks with expensive uplinks and time-sensitive use cases. In this paper, we contribute two LwM2M extensions to enable client-to-client (C2C) communication: (i) an authorization mechanism for clients, and (ii) an extended management interface to allow secure C2C access to resources. We analyse the security properties of the proposed extensions and show that they are compliant with LwM2M security requirements. Our performance evaluation on off-the-shelf IoT hardware shows that C2C communication outperforms server-centric deployments. First, LwM2M deployments with edge C2C communication yield a ~90% faster notification delivery and ~8x greater throughput compared to common server-centric scenarios, while keeping a small memory overhead of ~8%. Second, in server-centric communication, the delivery rate degrades when resource update intervals drop below 100 ms.

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arXiv2021

Transparent Forwarders: An Unnoticed Component of the Open DNS Infrastructure

In this paper, we revisit the open DNS (ODNS) infrastructure and, for the first time, systematically measure and analyze transparent forwarders, DNS components that transparently relay between stub resolvers and recursive resolvers. Our key findings include four takeaways. First, transparent forwarders contribute 26% (563k) to the current ODNS infrastructure. Unfortunately, common periodic scanning campaigns such as Shadowserver do not capture transparent forwarders and thus underestimate the current threat potential of the ODNS. Second, we find an increased deployment of transparent forwarders in Asia and South America. In India alone, the ODNS consists of 80% transparent forwarders. Third, many transparent forwarders relay to a few selected public resolvers such as Google and Cloudflare, which confirms a consolidation trend of DNS stakeholders. Finally, we introduce DNSRoute++, a new traceroute approach to understand the network infrastructure connecting transparent forwarders and resolvers.

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arXiv2021

Spoki: Unveiling a New Wave of Scanners through a Reactive Network Telescope

Large-scale Internet scans are a common method to identify victims of a specific attack. Stateless scanning like in ZMap has been established as an efficient approach to probing at Internet scale. Stateless scans, however, need a second phase to perform the attack, which remains invisible to network telescopes that only capture the first incoming packet and is not observed as a related event by honeypots. In this work, we examine Internet-wide scan traffic through Spoki, a reactive network telescope operating in real-time that we design and implement. Spoki responds to asynchronous TCP SYN packets and engages in TCP handshakes initiated in the second phase of two-phase scans. Because it is extremely lightweight it scales to large prefixes where it has the unique opportunity to record the first data sequence submitted within the TCP handshake ACK. We analyze two-phase scanners during a three months period using globally deployed Spoki reactive telescopes as well as flow data sets from IXPs and ISPs. We find that a predominant fraction of TCP SYNs on the Internet has irregular characteristics. Our findings also provide a clear signature of today's scans as: (i) highly targeted, (ii) scanning activities notably vary between regional vantage points, and (iii) a significant share originates from malicious sources.

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arXiv2021

Simulation-based Evaluation of a Synchronous Transaction Model for Time-Sensitive Software-Defined Networks

Real-time networks based on Ethernet require robust quality-of-service for time-critical traffic. The Time-Sensitive Networking (TSN) collection of standards enables this in real-time environments like vehicle on-board networks. Runtime reconfigurations in TSN must respect the deadlines of real-time traffic. Software-Defined Networking (SDN) moves the control plane of network devices to the SDN controller, making these networks programmable. This allows reconfigurations from a central point in the network. In this work, we present a transactional model for network reconfigurations that are synchronously executed in all network devices. We evaluate its performance in a case study against nontransactional reconfigurations and show that synchronous transactions enable consistency for reconfigurations in TSN without increased latencies for real-time frames.

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arXiv2021

The Far Side of DNS Amplification: Tracing the DDoS Attack Ecosystem from the Internet Core

In this paper, we shed new light on the DNS amplification ecosystem, by studying complementary data sources, bolstered by orthogonal methodologies. First, we introduce a passive attack detection method for the Internet core, i.e., at Internet eXchange Points (IXPs). Surprisingly, IXPs and honeypots observe mostly disjoint sets of attacks: 96% of IXP-inferred attacks were invisible to a sizable honeypot platform. Second, we assess the effectiveness of observed DNS attacks by studying IXP traces jointly with diverse data from independent measurement infrastructures. We find that attackers efficiently detect new reflectors and purposefully rotate between them. At the same time, we reveal that attackers are a small step away from bringing about significantly higher amplification factors (14x). Third, we identify and fingerprint a major attack entity by studying patterns in attack traces. We show that this entity dominates the DNS amplification ecosystem by carrying out 59% of the attacks, and provide an in-depth analysis of its behavior over time. Finally, our results reveal that operators of various .gov names do not adhere to DNSSEC key rollover best practices, which exacerbates amplification potential. We can verifiably connect this operational behavior to misuses and attacker decision-making.

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arXiv2021

QUICsand: Quantifying QUIC Reconnaissance Scans and DoS Flooding Events

In this paper, we present first measurements of Internet background radiation originating from the emerging transport protocol QUIC. Our analysis is based on the UCSD network telescope, correlated with active measurements. We find that research projects dominate the QUIC scanning ecosystem but also discover traffic from non-benign sources. We argue that although QUIC has been carefully designed to restrict reflective amplification attacks, the QUIC handshake is prone to resource exhaustion attacks, similar to TCP SYN floods. We confirm this conjecture by showing how this attack vector is already exploited in multi-vector attacks: On average, the Internet is exposed to four QUIC floods per hour and half of these attacks occur concurrently with other common attack types such as TCP/ICMP floods.

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arXiv2021

A Reproducibility Study of "IP Spoofing Detection in Inter-Domain Traffic"

IP spoofing enables reflection and amplification attacks, which cause major threats to the current Internet infrastructure. Detecting IP packets with incorrect source addresses would help to improve the situation. This is easy at the attacker's network, but very challenging at Internet eXchange Points (IXPs) or in transit networks. In this reproducibility study, we revisit the paper \textit{Detection, Classification, and Analysis of Inter-Domain Traffic with Spoofed Source IP Addresses} published at ACM IMC 2017. Using data from a different IXP and from a different time, we were not able to reproduce the results. Unfortunately, our further analysis reveals structural problems of the state of the art methodology, which are not easy to overcome.

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arXiv2021

Reliable Firmware Updates for the Information-Centric Internet of Things

Security in the Internet of Things (IoT) requires ways to regularly update firmware in the field. These demands ever increase with new, agile concepts such as security as code and should be considered a regular operation. Hosting massive firmware roll-outs present a crucial challenge for the constrained wireless environment. In this paper, we explore how information-centric networking can ease reliable firmware updates. We start from the recent standards developed by the IETF SUIT working group and contribute a system that allows for a timely discovery of new firmware versions by using cryptographically protected manifest files. Our design enables a cascading firmware roll-out from a gateway towards leaf nodes in a low-power multi-hop network. While a chunking mechanism prepares firmware images for typically low-sized maximum transmission units (MTUs), an early Denial-of-Service (DoS) detection prevents the distribution of tampered or malformed chunks. In experimental evaluations on a real-world IoT testbed, we demonstrate feasible strategies with adaptive bandwidth consumption and a high resilience to connectivity loss when replicating firmware images into the IoT edge.

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arXiv2021

PHiLIP on the HiL: Automated Multi-platform OS Testing with External Reference Devices

Developing an operating system (OS) for low-end embedded devices requires continuous adaptation to new hardware architectures and components, while serviceability of features needs to be assured for each individual platform under tight resource constraints. It is challenging to design a versatile and accurate heterogeneous test environment that is agile enough to cover a continuous evolution of the code base and platforms. This mission is even morehallenging when organized in an agile open-source community process with many contributors such as for the RIOT OS. Hardware in the Loop (HiL) testing and Continuous Integration (CI) are automatable approaches to verify functionality, prevent regressions, and improve the overall quality at development speed in large community projects. In this paper, we present PHiLIP (Primitive Hardware in the Loop Integration Product), an open-source external reference device together with tools that validate the system software while it controls hardware and interprets physical signals. Instead of focusing on a specific test setting, PHiLIP takes the approach of a tool-assisted agile HiL test process, designed for continuous evolution and deployment cycles. We explain its design, describe how it supports HiL tests, evaluate performance metrics, and report on practical experiences of employing PHiLIP in an automated CI test infrastructure. Our initial deployment comprises 22 unique platforms, each of which executes 98 peripheral tests every night. PHiLIP allows for easy extension of low-cost, adaptive testing infrastructures but serves testing techniques and tools to a much wider range of applications.

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arXiv2021

A Guideline on Pseudorandom Number Generation (PRNG) in the IoT

Random numbers are an essential input to many functions on the Internet of Things (IoT). Common use cases of randomness range from low-level packet transmission to advanced algorithms of artificial intelligence as well as security and trust, which heavily rely on unpredictable random sources. In the constrained IoT, though, unpredictable random sources are a challenging desire due to limited resources, deterministic real-time operations, and frequent lack of a user interface. In this paper, we revisit the generation of randomness from the perspective of an IoT operating system (OS) that needs to support general purpose or crypto-secure random numbers. We analyse the potential attack surface, derive common requirements, and discuss the potentials and shortcomings of current IoT OSs. A systematic evaluation of current IoT hardware components and popular software generators based on well-established test suits and on experiments for measuring performance give rise to a set of clear recommendations on how to build such a random subsystem and which generators to use.

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